Diastereodivergent organocatalysis for the asymmetric synthesis of chiral annulated furans† †Electronic supplementary information (ESI) available: Complete experimental procedures and full compound characterisation, including HPLC traces and NMR spectra (PDF). CCDC 1046068 and 1046069. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc01052g

Disclosed herein is a stereoselective method for the synthesis of 2,3-furan fused carbocycles bearing adjacent quaternary and tertiary carbon stereocenters. The chemistry is based on an asymmetric addition of b-ketoesters to 2-(1-alkynyl)-2-alkene-1-ones catalysed by natural cinchona alkaloids followed by a silver-catalysed intramolecular cycloisomerisation. By exploiting the distinct catalysis modes of quinine, which can act either as a general base or, upon opportune modifications, as a phase transfer catalyst, a complete switch of the enforced sense of diastereoinduction is achieved. The stereodivergent systems enable access to the full matrix of all possible stereoisomeric products.